Jazz Bass cavitys

I have two jazz basses a MIM standard and a MIA standard and they both have a big route from the controls to the bridge pickup when I take the scratch plate off. I was wondering if theres any way I can shield this hole in order to put on the ashtray pickup covers as I bought the covers or ebay before finding out that I wouldn't be able to fit both on. What can I do? cheers
rowan.

What I am talking about is not the pickup covers as far as the ACTUAL pickup cover but the chrome ashtray pickup cover or what ever it is called. I want to have the cover on like the Marcus Miller bass but I can not screw it in on the right side as there is the cavity there. I was wondering if there was anything I can put in the cavity so I can screw in the chrome ashtray pickup cover.

I believe your bridge pickup should have all wood around it unless you're confusing the bridge with the neck, I've never put on on the neck side so I wouldn't know if the hole matches up with the routing orwhatever but I do believe your route curves downward into the control plate area so you should be able to fit both on fine